1. Field of the invention
The present invention refers to a storage apparatus apt to preserve an ink jet printhead of the interchangeable cartridge type, insertable on devices generating images on a medium, after the former has been removed from its packaging and possibly already partially used on the device.
The storage apparatus maintains the area of the said printhead bearing the nozzles for discharging the ink droplets (called ejector plate) substantially sealed inside an environment impregnated with humidity in such a way as to prevent evaporation and coagulation of said ink with consequent occlusion of the nozzles, even if the printhead is not used for prolonged periods of time.
2. Description of the Prior Art
Devices are known in the current art for generation of images on a medium, generally sheets of paper or other suitable material, for example ink jet printers, using interchangeable printheads of the monobloc, disposable cartridge type, i.e. with an ink reservoir integrated within the printhead, or of the "refillable" cartridge type, i.e. with an ink reservoir that can be replaced.
The printheads may contain a black (or generically monochromatic) ink, or three inks of different colours in the reservoir, thus permitting, simply by changing the printhead, printing in black or in colour with the same printer, which provides considerable flexibility and variety of use.
On these types of printer, or more exactly in the printhead carriage thereof, a single printhead at a time may be resident, so that users are faced with the problem of having at least one printhead, sometimes the monochromatic type, at other times the colour type, still partially filled with ink and functioning perfectly, that has to be preserved in a suitable container to avoid it from deteriorating during the periods in which it is not used to the extent that it may become no longer functional or in some way defective.
In fact, the characteristics of the ink and the dimensions of the nozzles from which the ink droplets are ejected during printing are such that, if the printhead is left for even relatively short periods of time with the ejector plate thereof exposed to the surrounding environment, the ink coagulates, thereby occluding the nozzles and the printhead becomes unusable.
The danger thereof is so great that the ink jet printers known in the current art are equipped with what is known as a "service station", one of the declared objects of which is to protect and isolate the nozzles from the surrounding environment whenever the printhead is not functioning, even in the time intervening between printing of one sheet and the next should this interval exceed a given, predetermined time.
Martin et al., in U.S. Pat. No. 5,155,497, describe one of these "service stations", interchangeably adaptable, through the rotation of a support, for protecting a printhead for black printing or alternatively a printhead for colour printing, and which comprises a cap that encloses the ejector plate, isolating it from the external environment in such a way as to prevent coagulation of the ink and contamination of the nozzles by dust.
This eliminates the problem for the printhead remaining on board the printer carriage, but it is evident that, if the user of the printer concurrently has two different types of interchangeable printhead in usage, the problem still remains of preserving that printhead which is momentarily not fitted in the printhead carriage of the printer.
The most frequent case, and the one to which reference shall be made hereinafter in the disclosure of this invention, but which is by no means limiting, is that in which the printer can work interchangeably with a printhead for black printing (the type most commonly used, for example, to print texts) or with a printhead for colour printing (containing three coloured inks and used mainly for graphic printing): when the printer uses the printhead for black printing, the printhead for colour printing must be preserved externally to the printer under proper conditions, and vice versa when the printer uses the printhead for colour printing.
To solve this specific problem, dedicated storage apparatuses have been constructed, such as, for example, that described by Kawai et al. in European Patent Application No. EP 560266, in which a container comprises within a cap similar to that described in the Martin et al. Patent cited above, a cap which comes into contact with the ejector plate of the printhead in such a way as to seal it, and is further connected to a member that is capable of absorbing any ink seeping out of the nozzles, for example following variations in ambient temperature or pressure.
The dimensions of the cap, generally formed of a synthetic rubber with low gas permeability and in particular of EPDM, must be calculated correctly in function of the type of printhead to which the cap will be coupled, this to guarantee the effective sealing properties of the device; usually, the dimensions of the ejector plate on printheads for black printing and of the ejector plate on those for colour printing are different, because of the different number of nozzles and consequently, a cap suitable for a printhead for black printing may not also be fit for use on a printhead for colour printing, and vice versa.
Containers for preserving interchangeable printheads are known in the current art, comprising two distinct and independent cavities, one capable of receiving only a printhead for black printing, and the other capable of receiving only a printhead for colour printing; accordingly however, encumbrance of the container is considerable and users must take care to insert the right printhead in its proper cavity.